Metal regulation of metallothionein participation in redox reactions.

Like glutathione or dithiothreitol, metallothionein effects the formation of pancreatic ribonuclease A from its S-sulfonated derivative catalyzed by protein disulfide isomerase. EDTA increases the yield of ribonuclease A activity recovery with metallothionein but does not affect the reaction with glutathione or dithiothreitol. EDTA also increases the reactivity of thiol groups in metallothionein with 5,5'-dithiobis-(2-nitrobenzoic acid) by chelation of zinc ions. It is suggested that the thiol groups in metallothionein form a part of the pool of cellular thiols in the regulation of cellular redox reactions and their availability is modulated by zinc chelation.